1. Field of the Invention
The present invention relates to an electrodeless lighting system, and particularly, to a middle output electrodeless lighting system configured to apply a magnetic field to an electrodeless bulb to improve luminous efficiency.
2. Description of the Background Art
In general, an electrodeless lighting system is an apparatus emitting visible light or ultraviolet light from an electrodeless plasma bulb upon applying microwave energy to the bulb. The electrodeless lighting system has a long life span and good lighting effect compared with an incandescent lamp or a fluorescent lamp which is generally used.
Such an electrodeless lighting system is classified into high output, middle output and low output according to its usage and output extent.
FIG. 1 is a longitudinal sectional view showing one example of a conventional middle output electrodeless lighting system.
As shown, the conventional middle output electrodeless lighting system using microwave energy comprises: a case 1 forming a certain internal space; a microwave generator 2 mounted in the case 1, for generating microwave energy; a high voltage generator 3 raising common AC power to a high voltage and supplying the high voltage to the microwave generator 2; a waveguide 4 for guiding microwave energy generated at the microwave generator 2; a resonator 6 installed at an exit portion 4a of the waveguide 4, communicating with the waveguide 4; and a bulb 5 positioned in the resonator 6, for generating light as a filling material becomes a plasma by the microwave energy transferred through the waveguide 4.
In addition, a reflecting mirror 7 for concentratively reflecting light generated at the bulb 5 to the front is provided in front of the case 1, namely, at a peripheral area of the resonator 6.
A dielectric mirror 8 which passes microwave energy transferred through the waveguide 4 and reflects light emitted from the bulb 5 to the front is installed in the exit portion 4a of the waveguide 4. A hole 8a is formed at a central portion of the dielectric mirror 8, so that a shaft portion 9 of the bulb 5 penetrates therethrough.
Meanwhile, a cooling fan 10 for cooling the microwave generator 2 and the high voltage generator 3 is provided at the rear of the case 1. And, non-explained reference numeral 11 is a fan motor, and 12 is a bulb motor for rotating the bulb 5.
The conventional middle output electrodeless lighting system having such a structure is operated in the following manner.
When a driving signal is inputted to the high voltage generator 3, the high voltage generator 3 raises AC power and supplies a raised high voltage to the microwave generator 2, and the microwave generator 2 is oscillated by the high voltage, thereby generating microwave energy having a very high frequency. The microwave energy generated in such a manner is guided through the waveguide 4 and is emitted into the resonator 6. The emitted microwave energy resonates in the resonator 6, forming an electric field and strongly being applied to a portion where the bulb 5 of the resonator 6 is placed. At this time, a filling material within the bulb 5 is electrically discharged, thereby generating light having a specific spectrum. This light is reflected to the front by the reflecting mirror 7 and the dielectric mirror, thereby lightening a space.
However, the conventional middle output electrodeless lighting system constructed as above uses a bulb having a volume of about 50% of a volume of a bulb used for a high output electrodeless lighting system. Since the volume of the bulb of the middle output electrodeless lighting system is smaller than that of the high output one, the amount of a filling material filled therein is also decreased. Accordingly, initial lighting is not easily achieved, and thus luminous efficiency of the entire electrodeless lighting system is degraded.